Warning lights, i.e., visual notification appliances, are often used within buildings in conjunction with audio warning alarms so that the hearing impaired can be alerted to emergency conditions such as a fire. Typically, the warning light includes a flashing bulb positioned horizontally or vertically within a reflector. The bulb receives power from a power supply in a control panel. This power supply is normally powered by the building's AC supply, but also provides battery backup to ensure that the warning light will have power in the event power to the building is disrupted.
Warning lights are subject to light intensity requirements as specified in various standards, such as Underwriters Laboratories UL 1971 (as well as UL 1638), “Standard for Safety Signalling Devices for the Hearing Impaired,” and the National Fire Protection Association's NFPA 72, The National Fire Alarm Code, all of which are incorporated herein by reference in their entirety.
The required intensity of the strobe, measured in candela, is dependent on occupancy, location, and local and national codes, standards and guidelines. For example, a strobe that is in a sleeping area and is required to wake the occupants is required to put out more candela than a strobe located in a hallway.
U.S. Pat. No. 6,411,201 to Hur et al., describes a notification appliance that provides multiple candela settings. A “menu” on the device provides the available strobe intensity settings. An installer can select a setting by positioning an actuator such that the actuator indicates the selection. The actuator engages a selector switch so that lateral movement of the actuator is translated to the selector switch.